Some Trace Metals Such as Molybdenum and Rhenium Are Soluble

question 161

Multiple Choice

Some trace metals such as molybdenum and rhenium are soluble in oxygenated water.These rare metals first appeared in sedimentary rocks on Earth 2.5 billion years ago, where previously they occurred as chemical compounds in minerals.The appearance of these metals at this time indicates that

• A) cyanobacteria used all available oxygen until 2.5 billion years ago.
• B) meteorites from Mars carried oxygen to Earth.
• C) comets brought oxygen to Earth.
• D) there was no life on Earth until 2.5 billion years ago.
• E) there was no atmospheric oxygen on Earth until 2.5 billion years ago.

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